请基于pygame，设计以下游戏底层代码：一个吃豆人，在迷宫里不断吃豆豆，每次一颗豆豆都将获得一分，在迷宫内有一个大魔王追击吃豆人，吃豆人被追上后，游戏结束

好的，让我来回答你的问题。以下是基于pygame的游戏底层代码实现：

import pygame
import random

# 初始化pygame
pygame.init()

# 设置游戏屏幕大小
WINDOW_WIDTH = 640
WINDOW_HEIGHT = 480
screen = pygame.display.set_mode((WINDOW_WIDTH, WINDOW_HEIGHT))

# 设置游戏标题
pygame.display.set_caption("吃豆人游戏")

# 设置颜色
BLACK = (0, 0, 0)
WHITE = (255, 255, 255)
RED = (255, 0, 0)
GREEN = (0, 255, 0)

# 加载图片
player_img = pygame.image.load('player.png')
ghost_img = pygame.image.load('ghost.png')
bean_img = pygame.image.load('bean.png')

# 设置游戏参数
player = {'rect': player_img.get_rect(), 'dir': 'left'}
bean_list = []
ghost_x = WINDOW_WIDTH / 2
ghost_y = WINDOW_HEIGHT / 2
score = 0

# 创建迷宫地图
MAP_WIDTH = WINDOW_WIDTH // 20
MAP_HEIGHT = WINDOW_HEIGHT // 20
maze = [[0 for y in range(MAP_HEIGHT)] for x in range(MAP_WIDTH)]

# 定义迷宫对象
class Maze:
  def __init__(self, maze):
    self.maze = maze

  # 画迷宫地图
  def draw(self):
    for x in range(MAP_WIDTH):
      for y in range(MAP_HEIGHT):
        if self.maze[x][y] == 1:
          rect = pygame.Rect(x * 20, y * 20, 20, 20)
          pygame.draw.rect(screen, WHITE, rect)

# 创建吃豆人对象
class Player:
  def __init__(self, rect):
    self.rect = rect

  # 移动吃豆人
  def move(self, dir):
    if dir == 'left':
      self.rect.left -= 20
    elif dir == 'right':
      self.rect.left += 20
    elif dir == 'up':
      self.rect.top -= 20
    elif dir == 'down':
      self.rect.top += 20

  # 吃豆豆
  def eat_bean(self, beans):
    global score
    for index, bean in enumerate(beans):
      if self.rect.colliderect(bean['rect']):
        score += 1
        del beans[index]

  # 判断是否碰到魔王
  def is_collide_ghost(self, ghost_rect):
    if self.rect.colliderect(ghost_rect):
      return True
    else:
      return False

# 创建豆豆对象
class Bean:
  def __init__(self, rect):
    self.rect = rect

  # 画豆豆
  def draw(self):
    screen.blit(bean_img, self.rect)

# 创建魔王对象
class Ghost:
  def __init__(self, x, y):
    self.rect = ghost_img.get_rect(center=(x, y))
    self.dir = 'left'

  # 移动魔王
  def move(self):
    if self.dir == 'left':
      self.rect.left -= 10
      if self.rect.left < 0:
        self.dir = 'right'
    elif self.dir == 'right':
      self.rect.left += 10
      if self.rect.right > WINDOW_WIDTH:
        self.dir = 'left'

  # 画魔王
  def draw(self):
    screen.blit(ghost_img, self.rect)

# 随机生成豆豆
def generate_beans():
  global bean_list
  for i in range(20):
    x = random.randint(0, MAP_WIDTH - 1)
    y = random.randint(0, MAP_HEIGHT - 1)
    if maze[x][y] == 0:
      rect = pygame.Rect(x * 20 + 5, y * 20 + 5, 10, 10)
      bean_list.append({'bean': Bean(rect), 'rect': rect})

# 创建吃豆人对象
player = Player(player['rect'])

# 创建迷宫对象
maze_obj = Maze(maze)

# 创建魔王对象
ghost = Ghost(ghost_x, ghost_y)

# 随机生成豆豆
generate_beans()

# 游戏循环
running = True
while running:
  # 将背景设为黑色
  screen.fill(BLACK)

  # 处理游戏事件
  for event in pygame.event.get():
    if event.type == pygame.QUIT:  # 点击关闭按钮
      running = False
    elif event.type == pygame.KEYDOWN:
      if event.key == pygame.K_LEFT:  # 吃豆人向左移动
        player.move('left')
      elif event.key == pygame.K_RIGHT:  # 吃豆人向右移动
        player.move('right')
      elif event.key == pygame.K_UP:  # 吃豆人向上移动
        player.move('up')
      elif event.key == pygame.K_DOWN:  # 吃豆人向下移动
        player.move('down')

  # 画迷宫地图
  maze_obj.draw()

  # 移动魔王
  ghost.move()

  # 判断是否碰到魔王
  if player.is_collide_ghost(ghost.rect):
    running = False

  # 画魔王
  ghost.draw()

  # 吃豆豆
  player.eat_bean(bean_list)

  # 画豆豆
  for bean in bean_list:
    bean['bean'].draw()

  # 画吃豆人
  screen.blit(player_img, player.rect)

  # 显示得分
  font = pygame.font.Font(None, 36)
  score_text = font.render("Score: {}".format(score), True, GREEN)
  screen.blit(score_text, (10, 10))

  # 刷新屏幕
  pygame.display.flip()

# 退出游戏
pygame.quit()

上述代码实现了一个基于pygame的吃豆人游戏，您可以根据需求进行修改和优化。